Heating rollers with axial magnetic force reduction means

ABSTRACT

In a heating roller of the class comprising a cup-shaped cylindrical roller having a closed bottom, a driving shaft for rotating the roller connected to the center of the bottom and extending coaxially through the cylindrical roller, a stationary bobbin supported within the cylindrical roller coaxially with the driving shaft, the bobbin having an inner flange facing to the bottom and an outer flange close to the open end of the cupshaped cylindrical roller, and an induction coil wound about the bobbin for inductively heating the cylindrical roller, there are provided a radially extending flange at the open end of the cupshaped cylindrical roller and a surrounding annular ring connected to the periphery of the outer flange to surround the radially extending flange.

United States a t'ent 1191 Arita [s41 HEATING ROLLERS wmr AXIAL MAGNETICFORCE REDUCTHON MEANS [76'] inventor: Koshei Arita, 10,23 2-ch0me,Minamimagone, Ohota-ku, Tokyo, Japan [22] Filed: 1 Mar. 23, 1972 [21]App]. No.: 237,249

[52] US. Cl ..2l9/10.49, 219/1061 [51] Int. Cl. ..H05b 5/08 [58] Fieldof Search..'...; ..219/10.49, 10.61,

[56] References Cited UNITED STATES: PATENTS 3,412,229 11/1968Seagrave....- ..2l9/10.61 2,273,423 2 1942 Somes ..219/1049 [451 May 1,1973 Primary Examiner-J. V. Truhe Assistant Examiner-B. A. ReynoldsAtt0rney-Char1es W. Helze'r 57] ABSTRACT In a heating roller of theclass comprising a cupshaped cylindrical roller having a closed bottom,a driving shaft for rotating the roller connected to the center of thebottom and extending coaxially through the cylindrical roller, astationary bobbin supported within the cylindrical roller coaxially withthe driving shaft, the bobbin having an inner flange facing to thebottom and an outer flange close to the open end of the cup-shapedcylindrical roller, and an induction coil wound about the bobbin forinductively heating the cylindrical roller, there are provided aradially extending flange at the open end of the cup-shaped cylindricalroller and a surrounding annular ring connected to the periphery of theouter flange to surround the radially extending flange.

7 Claims, 4 Drawing Figures HEATING ROLLERS WITH AXIAL MAGNETIC FORCEREDUCTION MEANS BACKGROUND OF INVENTION 1. Field oflnvention Thisinvention relates to an improved construction for a heating rolleradapted to heat synthetic fibers or strings which are are required to beheat treated at a constant temperature.

2. Prior Art Problem As shown in FIG. 1, a conventional heating rollerutilized for this purpose comprises a cup-shaped cylindrical roller 1having one end (left hand end as viewed in FIG. 1) closed and providedwith a driving shaft 2 connected to the center of the bottom. Althoughnot shown in the drawing, the shaft 2 is supported by a bearing andconnected to a source of drive. The inner surface of the cylindricalroller 1 is covered by a heat generating layer 3 of conductive material.A cylindrical bobbin 4 having an inner flange 4 and an outer flange 4 isprovided to concentrically surround driving shaft 2. The outer diameterof inner flange 4 is made smaller than the inner diameter of thecylindrical roller 1 whereas the outer flange 4 has an outer diametersubstantially equal to that of the cup-shaped cylindrical roller 1 andis positioned opposite the open end thereof with a small gap gtherebetween. On the outside of the bobbin 4 are mounted a laminatedmagnetic core 5 and an induction coil 6 which is energized by a sourceof aland outer flange 4 are made ofmagnetic material so as to form asubstantially closedmagnetic circuit.

When the induction coil 6 "is energized from the source of AC, magneticflux' is induced to flow through the magnetic path indicated by dottedlines thereby heating the cylindrical roller by the eddy current lossand hysteresis loss produced therein, the heating being across the gap gbetween the opening of the cylindrical roller 1 and the outer flange 4and the gap g; between the inner bottom surface of the cylindricalroller 1 and the inner flange 4, of the bobbin 4, thrust loads actternating current (not shown). The cylindrical roller 1 upon the shaft 2inthe directions shown by arrows a I and a Since these thrust loadsoperate cumulatively, the shaft will be biased by the resultant of thesethrust loads to the right as viewed in FIG. 1.

Bm and 19m the flux densities at the gaps g, and g and no thepermeability of air. The resultant F of these attractive forces, that isthe thrust load acting upon shaft 2 in the direction of the arrows isexpressed by the following equation.

F= F F l/2p.o) (S,Bm, S Bm [N] Accordingly, when the induction coil 6 isenergized by a sine'wave alternating current, the thrust load-fluctuatessinusoidally and canresult in damaging the bearing of the shaft 2. Wherethebearing is damaged heavily, the coil 6 also might be damaged.

SUMMARY or INvENTIoN It is an object of this invention to provide animproved heating roller which is free from the axial thrust describedabove.

Accordingly, to this invention there is provided a heating roller of theclass comprising a cup-shaped cylindrical roller having a closed bottom,a driving shaft connected to the center of the bottom and extendingcoaxially through the cylindrical roller, a stationary bobbin containedin the cylindrical roller coaxially with the driving shaft, the bobbinhaving an inner flange facing the bottom and an outer flange close tothe open end of the cup-shaped cylindrical roller, and an induction coilwound about the bobbin for inductively heating the cylindrical roller.The invention is characterized in that there are provided a radiallyextending flange at the open end of the cup-shaped cylindrical rollerand a surrounding annular ring connected to the periphery of the outerflange and surrounding v the radially extending flange.

BRIEF DESCRIPTION or DRAWINGS DESCRIPTION OF THE PREFERRED r EMBODIMENTFIGS. 3 and 4 show one embodiment of the present invention in whichportions corresponding to parts of the heated roller shown and describedwith relation to FIGS. 1 and 2 are designated by the same'referencecharacters. In this embodiment, the cylindrical roller 1 is providedwith a radially extending flange 1 at its open end and the outerdiameterof the outer-flange 4 of the bobbin 4 is considerably larger thanthat ofthe flange 1,. A surrounding annular ring 7 having a crosssectionalconfiguration of a letter L is secured to and extended as part of theouter end of flange 4 to surround the flange 1,. The axi al gaps betweenflanges 1 and 4 and 1, and 7 are represented by g and g,', respectively,while the axial gap between the bottom of the roller. 1 and the innerflange 4 of bobbin 4 is represented by g The flange 1 and annular ring 7are also made of magnetic material to form a magnetic path indicated bydotted lines.

With this construction, the attractive forces F and F at the gaps g andg create thrust loads in the direction of arrow bjust in the same manneras in the construction shown in FIG. 1. However, the attractive force F1 at gap 3 operates in the opposite direction as shown by arrow C. Thusthe force F counteractsthe sum of the forces (F F These attractiveforces are given by 1=( 1 1 /2I 2= 2 2 /2u 3=( 3 3 The relation F 1 F Fcan be readily satisfied by varying the cross-sectional areas 8,, S andS of the magnetic paths or the flux densities B B and B at therespective gaps g g and g;, by appropriate spacing of the gaps. For thispurpose, g and g may have a greater spacing than g With the improvedconstruction, since the flange 1 of the roller 1 is surrounded by theintumed L-shaped ring 7, the heated air inside the cylinder is retainedtherein thus improving the heat efficiency of the heating roller.

As above-described according to this invention there is provided animproved heating roller wherein the thrust acting upon the driving shaftcan be eliminated or substantially reduced by simple means.

While the invention has been shown and described in terms of a preferredembodiment it will be clear that many changes and modifications may bemade without departing from the true spirit and scope of the inventionas defined in the appended claims.

What is claimed is: 1

1. In a heating roller of the class comprising a rotatable cup-shapedcylindrical roller having a closed bottom, a driving shaft connected tothe center of the bottom and extending coaxially through said cup-shapedcylindrical roller for rotating said roller, a stationary bobbinsupported within said cup-shaped cylindrical roller coaxially with saiddriving shaft with said roller being freely rotatable relative to saidbobbin, said bobbin having an inner flange facing said bottom and anouter flange close tov the open end of said cup-shaped cylindricalroller, and an induction coil wound about said bobbin for producingmagnetic lines of flux magnetically coupling'said bobbin and said rollerthrough said flanges for inductively heating said cylindrical roller,the improvement which comprises, a radially extending flange secured tothe open end of said cupshaped cylindrical roller and a surroundingannular ring connected to the periphery of the outer flange of saidbobbin and surrounding said radially extending flange for producingcounter-balancing magnetic forces acting between the roller and thebobbin.

2. A heating roller according to claim 1 wherein a short circuitedconductive ring is provided on the cylindrical surface of saidcup-shaped cylindrical roller to induce heating current.

3. A heating roller according to claim 1 wherein the air gap between thebottom of said cup-shaped cylindrical roller and said inner flange ofsaid bobbin and the air gap between said radially extending flange ofsaid cylindrical roller and the outer flange of said bobbin create axialmagnetic forces acting in the same direction and the air gap betweensaid surrounding annu'lar ring and said radially extending flangecreates an axial magnetic force counteracting said first mentionedmagnetic forces.

4. A heating roller according to claim 3 wherein at least the air gapbetween the radially extending flange of the cylindrical roller and theouter flange of the bob bin is greater than the air gap between thesurrounding annular ring and the radially extending flange.

5. A heating roller according to claim 3 wherein a short circuitedconductive ring is provided on the cylindrical surface of saidcup-shaped cylindrical roller to induce heating current, the surroundingannular ring has a cross-sectional configuration of a letter L with thebottom of the L-shaped ringe opposing and acting against the bottom sideof the radial y extending flange on said roller.

6. A heating roller according to claim 6 wherein at least the air gapbetween the radially extending flange of the cylindrical roller and theouter flange of the bobbin is greater than the air gap between thesurrounding annular ring and the radially extending flange.

7. A heating roller according to claim 1 wherein the surrounding annularring has a cross-sectional configuration of a letter L with the bottomof the L-shaped ring opposing and acting against the bottom said of theradially extending flange on said roller.

1. In a heating roller of the class comprising a rotatable cupshapedcylindrical roller having a closed bottom, a driving shaft connected tothe center of the bottom and extending coaxially through said cup-shapedcylindrical roller for rotating said roller, a stationary bobbinsupported within said cup-shaped cylindrical roller coaxially with saiddriving shaft with said roller being freely rotatable relative to saidbobbin, said bobbin having an inner flange facing said bottom and anouter flange close to the open end of said cup-shaped cylindricalroller, and an induction coil wound about said bobbin for producingmagnetic lines of flux magnetically coupling said bobbin and said rollerthrough said flanges for inductively heating said cylindrical roller,the improvement which comprises, a radially extending flange secured tothe open end of said cupshaped cylindrical roller and a surroundingannular ring connected to the periphery of the outer flange of saidbobbin and surrounding said radially extending flange for producingcounterbalancing magnetic forces acting between the roller and thebobbin.
 2. A heating roller according to claim 1 wherein a shortcircuited conductive ring is provided on the cylindrical surface of saidcup-shaped cylindrical roller to induce heating current.
 3. A heatingroller according to claim 1 wherein the air gap between the bottom ofsaid cup-shaped cylindrical roller and said inner flange of said bobbinand the air gap between said radially extending flange of saidcylindrical roller and the outer flange of said bobbin create axialmagnetic forces acting in the same direction and the air gap betweensaid surrounding annular ring and said radially extending flange createsan axial magnetic force counteracting said first mentioned magneticforces.
 4. A heating roller according to claim 3 wherein at least theair gap between the radially extending flange of the cylindrical rollerand the outer flange of the bobbin is greater than the air gap betweenthe surrounding annular ring and the radially extending flange.
 5. Aheating roller according to claim 3 wherein a short circuited conductivering is provided on the cylindrical surface of said cup-shapedcylindrical roller to induce heating current, the surrounding annularring has a cross-sectional configuration of a letter L with the bottomof the L-shaped ringe opposing and acting against the bottom side of theradially extending flange on said roller.
 6. A heating roller accordingto claim 6 wherein at least the air gap between the radially extendingflange of the cylindrical roller and the outer flange of the bobbin isgreater than the air gap between the surrounding annular ring and theradially exteNding flange.
 7. A heating roller according to claim 1wherein the surrounding annular ring has a cross-sectional configurationof a letter L with the bottom of the L-shaped ring opposing and actingagainst the bottom said of the radially extending flange on said roller.